Trabecular Metal cups for acetabular defects with 50% or less host bone contact

Abstract

Acetabular component revision in the context of large contained bone defects with less than 50% host bone contact traditionally have been treated with roof reinforcement or antiprotrusio cages. Trabecular Metal cups (Zimmer, Inc, Warsaw, IN) may offer a reasonable treatment alternative. We evaluated the clinical and radiographic outcome of this mode of treatment. We prospectively followed 53 hip revision acetabular arthroplasty procedures performed with Trabecular Metal cups for contained defects with 50% or less contact with native bone. All patients were clinically and radiographically evaluated for evidence of loosening or failure. Minimum followup was 24 months (average, 45 months; range, 24-71 months). Contact with host bone ranged from 0% to 50% (average, 19%). The mean postoperative Merle d'Aubigne-Postel score was 10.6 (range, 1-12), with a mean improvement of 5.2 (range, -4-10) compared to the preoperative score. Two failed cups (4%) were revised. Two additional cups (4%) had radiographic evidence of probable loosening. Complications included four dislocations and one sciatic nerve palsy. The data suggest treatment of cavitary defects with less than 50% host bone contact using Trabecular Metal cups, without structural support by augments or structural bone grafts, is a reasonable option.

Figures

Fig. 1

An intraoperative cup contact recording form is shown. The percentage of contact with host bone and morselized bone was recorded and drawn on the acetabular illustration.

Fig. 2A–D

(A) A 75-year-old patient had a cup revision after failure of an antiprotrusio cage. (B) She had a cavitary bone defect with 30% of host bone contact, and a TM cup was used. (C) Five months later, the cup failed and (D) was revised again using a cage.

Fig. 3A–B

(A) This 77-year-old patient had a revision of a failed roof ring. (B) Five years later, the TM cup was well fixed and the morselized allograft remodeled.